Reductant dosing system

ABSTRACT

A reductant dosing system for an engine is disclosed. The reductant dosing system may have a supply of reductant, a reservoir configured to hold pressurized reductant, and a pump configured to draw reductant from the supply and discharge reductant at an elevated pressure into the reservoir. The reductant dosing system may also have a plurality of injectors fluidly connected to the reservoir, and a drain valve fluidly connected between the reservoir and the supply.

TECHNICAL FIELD

The present disclosure is directed to a dosing system, and moreparticularly, to a reductant dosing system for use with an internalcombustion engine.

BACKGROUND

Internal combustion engines, including diesel engines, gasoline engines,gaseous fuel-powered engines, and other engines known in the art exhausta complex mixture of air pollutants. These air pollutants are composedof gaseous compounds including, among other things, the oxides ofnitrogen (NO_(X)). Due to increased awareness of the environment,exhaust emission standards have become more stringent, and the amount ofNO_(X) emitted to the atmosphere by an engine may be regulated dependingon the type of engine, size of engine, and/or class of engine.

In order to comply with the regulation of NO_(X), some enginemanufacturers have implemented a strategy called selective catalyticreduction (SCR). SCR is an exhaust treatment process where a reductant,most commonly urea ((NH₂)₂CO) or a water/urea solution, is selectivelyinjected into the exhaust gas stream of an engine and adsorbed onto adownstream substrate. The injected urea solution decomposes into ammonia(NH₃), which reacts with NO_(X) in the exhaust gas to form water (H₂O)and diatomic nitrogen (N₂). In order for SCR to be most effective, thereductant should be injected into the exhaust gas stream in a uniformlydistributed manner.

An exemplary reductant dosing system is disclosed in U.S. PatentPublication Number 2010/1039260 of Rodman et al. that published on Jun.10, 2010 (the '260 publication). Specifically, the '260 publicationdiscloses a fluid delivery system for supplying fluid to an exhauststream of a power source. The fluid delivery system includes a supplymanifold and a plurality of supply exit orifices fluidly linked to thesupply manifold. The exit orifices are arranged in an annularconfiguration around the exhaust stream to allow the fluid to flow fromthe manifold to the exhaust stream in a uniformly distributed manner.

SUMMARY

In accordance with one aspect, the present disclosure is directed towarda reductant dosing system. The reductant dosing system may include asupply of reductant, a reservoir configured to hold pressurizedreductant, and a pump configured to draw reductant from the supply anddischarge reductant at an elevated pressure into the reservoir. Thereductant dosing system may also include a plurality of injectorsfluidly connected to the reservoir, and a drain valve fluidly connectedbetween the reservoir and the supply.

According to another aspect, the present disclosure is directed towardanother reductant dosing system. This reductant dosing system mayinclude a supply of reductant, a reservoir configured to holdpressurized reductant, and a pump configured to draw reductant from thesupply and discharge reductant at an elevated pressure into thereservoir. The reductant dosing system may also include a plurality ofinjectors fluidly connected to the reservoir, and a controller incommunication with the plurality of injectors. The controller may beconfigured to activate the injectors to inject pressurized reductantwhen a pressure of reductant within the reservoir is a desired pressure.

According to still another aspect, the present disclosure is directedtoward a method of dosing reductant. The method may include drawingreductant from a low-pressure supply, pressurizing reductant, storingpressurized reductant, and simultaneously injecting stored reductant ata plurality of locations. The method may further include selectivelydraining stored reductant in response to one of a reductant pressure andan engine operational status.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an exemplary disclosed powersystem; and

FIG. 2 is a pictorial illustration of an exemplary disclosed reductantdosing system that may be used with the power system of FIG. 1.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary power system 10 having an engine 12 anda reductant dosing system 14. Engine 12 may be an internal combustionengine operable to combust fuel and produce a mechanical power outputand a flow of exhaust 15. The exhaust 15 from engine 12 may be directedthrough an aftertreatment component 16 to the atmosphere. In oneexample, aftertreatment component 16 may be a reduction catalystconfigured to reduce a constituent of the exhaust 15 in the presence ofa reductant to an acceptable level before discharge of the exhaust 15 tothe atmosphere. It is contemplated, however, that aftertreatmentcomponent 16 may also or alternatively embody an oxidation catalyst, aparticulate filter, or another aftertreatment component known in theart. Reductant dosing system 14 may be configured to supply thereductant utilized for the reduction process occurring withinaftertreatment component 16.

Reductant dosing system 14 may be configured to spray or otherwiseadvance reductant into the engine's exhaust 15 upstream ofaftertreatment component 16 to affect a reducing chemical reaction. Inone embodiment, reductant dosing system 14 may inject an urea solutioninto the exhaust 15 of engine 12 to affect selective catalytic reduction(SCR). The urea solution may include water (H₂O) and urea ((NH₂)₂CO). Attemperatures higher than about 180° C., the urea solution may decomposeinto ammonia (NH₃) that is used to convert NO_(x) (NO and NO₂) in theexhaust flow 15 of engine 12 to diatomic nitrogen (N₂) and water (H₂O).As shown in FIG. 2, reductant dosing system 14 may include a supply ofreductant 18, a reservoir 20 configured to hold pressurized reductant, apump 22 configured to draw reductant from supply 18 and dischargereductant at an elevated pressure into reservoir 20, a plurality ofinjectors 24 fluidly connected to reservoir 20, and a drain valve 26fluidly connected between reservoir 20 and supply 18.

Supply 18 may embody a low-pressure tank that is configured to holdreductant and fluidly connected via a supply passage 28 to a head member30 of pump 22. One or more check valves 32 may be disposed within supplypassage 28 at head member 30 to help ensure a unidirectional flow ofreductant from supply 18 into pump 22. In the disclosed embodiment,supply 18 may be located gravitationally lower than pump 22 tofacilitate gravity draining of supply passage 28, although otherarrangements are also contemplated. In some applications, supply 18 mayalso be connected to and periodically replenished by one or more remotetanks (not shown) having a larger capacity.

Reservoir 20 may embody an enclosed chamber mounted to and supported bypump 22 via head member 30. Reservoir 20 may be configured to store asmall quantity (e.g., an amount less than contained by supply 18) ofreductant that has been pressurized by pump 22. In one embodiment, thereservoir 20 include an elastomeric liner or barrier that allows thevolume thereof to expand to about ten times a combined maximum injectionamount of all injectors 24 during a single dosing event. This expandingvolume may help to dampen pressure pulsations caused by pumping andinjecting actions. It is contemplated that an external pulsationdampener may additionally or alternatively be connected to reservoir 20and/or that other volumes may also be utilized, if desired. A passage 34within head member 30 may fluidly connect reservoir 20 to pump 22, and acheck valve 36 may be disposed within passage 34 to help ensure aunidirectional flow of pressurized reductant from pump 22 to reservoir20.

Pump 22 may be a metering pump such as, for example, a diaphragm pump, acentrifuge pump, a piston pump, or a rotary pump. Pump 22 may beelectrically operated to draw low-pressure reductant from supply 18, andto pressurize the reductant to a desired level. Reductant pressurized bypump 22 may be directed past check valve 36 and through passage 34 intoreservoir 20. In one embodiment, pump 22 may be mounted to and supportedby an upper portion of supply 18. It is contemplated, however, that pump22 may be mounted separately and/or remotely from supply 18, if desired.

Injectors 24 may be generally located upstream of aftertreatmentcomponent 16 (referring to FIG. 1) and configured to independentlyinject reductant into the exhaust 15 flowing through aftertreatmentcomponent 16. In the example of FIGS. 1 and 2, reductant dosing system14 includes four separate injectors 24, although any number of injectors24 may be included. The four injectors 24 of the disclosed embodimentmay be disposed within an annular mounting member 38, for example anexhaust duct or manifold of engine 12, and distributed around the flowof exhaust 15 from engine 12. In one embodiment, the four injectors 24may be spaced about 90° apart. For example, a first injector 24 may bedisposed between the one and two o'clock positions, a second injector 24may be disposed between the four and five o'clock positions, a thirdinjector 24 may be disposed between the seven and eight o'clockpositions, and a fourth injector 24 may be disposed between the ten andeleven o'clock positions. Although other radial distributions ofinjectors 24 are considered, it should be noted that, in someapplications, it may be desirable to avoid injectors 24 being mounted atthe six o'clock position and pointing upwards, in order to reduce thelikelihood of reductant pooling and clogging in the vicinity of theinjectors 24. It is contemplated that injectors 24 may also be skewedrelative to each other along the longitudinal axis of the exhaust flow15, if desired, and/or be oriented with or against the flow of exhaust15.

Each injector 24 may embody an electronically operated spray nozzle thatincludes a valve element (not shown) movable from a closed orflow-blocking position at which no reductant passes into the exhaustflow 15, toward an open or flow-passing position at which a maximuminjection of reductant is achieved. The valve element of each injector24 may be independently moved to any position between the first andsecond positions to thereby vary the flow of reductant into the exhaust15 from engine 12. Based on a known pressure of the reductant and thevalve opening position of each injector 24, the flow rate of reductantfrom each injector 24 may be precisely controlled. It is contemplatedthat injectors 24 may alternatively be dependently controlled by thesame amount (i.e., controlled as a group), if desired. Injectors 24 maybe independently connected to reservoir 20 via individual reductantlines 42.

Mounting member 38 and/or injectors 24 may require cooling in someapplications to help inhibit reductant coking. Accordingly, in someapplications, reductant dosing system 14 may be fluidly connected toreceive a flow of coolant from engine 12. Specifically, a coolant jacket47 may be provided that at least partially surrounds or otherwisetransfers heat with mounting member 38 and/or injectors 24. Coolantjacket 47 may be connected to a coolant supply line 49 and a coolantdrain line 51 of engine 12 such that coolant from engine 12 may becirculated through coolant jacket 47, mounting member 38, and/orinjectors 24. It is contemplated that coolant jacket 47 may transferheat away from injectors 24 indirectly via mounting member 38 and/ordirectly through intimate contact of coolant with injectors 24, asdesired.

Drain valve 26 may be disposed within reservoir 20 and selectivelyenergized to control draining of reservoir 20. Specifically, drain valve26 may be disposed within a cavity 48 of reservoir 20 and include anupstream drain passage 50 and a downstream drain passage 52 connected tosupply passage 28 that facilitate fluid communication between reservoir20 and supply 18. Drain valve 26 may include a solenoid-actuated andspring-biased valve element that is movable between an open orflow-passing position and a closed or flow-blocking position based. Whendrain valve 26 is in the open position, reductant from reservoir 20 maypass through drain valve 26 to supply 18. When drain valve 26 is in theclosed position (shown in FIG. 2), the flow of reductant through drainvalve 26 may be inhibited. Drain valve 26, in the depicted embodiment,is spring-biased toward the open position.

One or more sensors and/or heaters may be associated with reductantdosing system 14 to provide indications as to the operation of reductantdosing system 14 or facilitate the operation thereof. For example, apressure sensor 54 may be associated with reservoir 20 and configured toprovide a signal indicative of a pressure of reductant therein. Atemperature sensor 56 may also be associated with reservoir 20 andconfigured to provide a signal indicative of a temperature of reductanttherein. A heater 58 may additionally be located within reservoir 20 andbe selectively energized to raise a temperature of reductant passingthrough reductant dosing system 14 to help prevent freezing orfacilitate thawing of the reductant. Other sensors and/or heaters (notshown) may similarly be associated with reductant pump 22 and/or supply18, if desired.

A controller 60 may be in communication with pump 22, injectors 24,drain valve 26, sensors 54 and 56, heater 58, and other components ofreductant dosing system 14 to regulate operation of reductant dosingsystem 14 in response to various input. Controller 60 may embody asingle or multiple microprocessors, field programmable gate arrays(FPGAs), digital signal processors (DSPs), etc. that include a means forcontrolling an operation of reductant dosing system 14 in response tothe signals received from sensors 54 and 56, from engine 12, fromaftertreatment component 16, and/or from other sources. Numerouscommercially available microprocessors can be configured to perform thefunctions of controller 60. It should be appreciated that controller 60could readily embody a microprocessor separate from that controllingother non-dosing related power system functions, or that controller 60could be integral with a general power system microprocessor and becapable of controlling numerous power system functions and modes ofoperation. If separate from the general power system microprocessor,controller 60 may communicate with the general power systemmicroprocessor via datalinks or other methods. Various other knowncircuits may be associated with controller 60, including power supplycircuitry, signal-conditioning circuitry, actuator driver circuitry(i.e., circuitry powering solenoids, motors, or piezo actuators), andcommunication circuitry.

Controller 60 may be in communication with pump 22 and injectors 24 toinitiate dosing events. In particular, controller 60 may be configuredto activate pump 22 to draw in reductant from supply 18, pressurize thereductant, and discharge the pressurized reductant at elevated pressuresinto reservoir 20 where the reductant is stored in anticipation ofdosing by injectors 24. Controller 60 may then selectively activate oneor all of injectors 24 to independently and simultaneously open andallow the pressurized reductant from reservoir 20 to spray into theexhaust flow 15 of engine 12 at a desired rate and/or with a desiredforce. It is contemplated that activation of pump 22 and/or injectors 24may be selectively initiated based on a pressure and/or temperature ofthe reductant within reservoir 20, based on an operational status orcondition of engine 12 and/or aftertreatment component 16, and/or basedon other conditions known in the art.

Controller 60 may also be in communication with drain valve 26 toinitiate draining events. Specifically, controller 60 may be configuredto move drain valve 26 to the flow-passing position under at least fourdifferent conditions. In a first condition, when a signal from pressuresensor 54 indicates that a pressure of reductant within reservoir 20 ishigher than desired, controller 60 may energize the solenoid of drainvalve 26 to cause drain valve 26 to open and pass pressurized reductantback to supply 18, thereby relieving the pressure within reservoir 20.Controller 60 may hold drain valve 26 in the flow-passing positionduring the overpressure condition until a signal from pressure sensor 54indicates that the pressure within reservoir 20 has been lowered to thedesired pressure. In one embodiment, the desired pressure may be about4-8 bar, with drain valve 26 opening at about 10-12 bar. In a secondcondition, when a signal from engine 12 indicates that engine 12 hasbeen turned off, controller 60 may again energize the solenoid of drainvalve 26 to move drain valve 26 to the flow-passing position, therebyallowing reductant within reservoir 20 to gravity-drain back to supply18. Controller 60 may maintain drain valve 26 in this flow-passingposition for a desired period of time corresponding with the emptying ofreservoir 20, until a signal from pressure sensor 54 indicates asufficiently low pressure within reservoir 20, or until anothercondition monitored by controller 60 has been satisfied. In a thirdcondition, when engine 12 has first been turned on or, alternatively, inpreparation for turning engine 12 on, controller 60 may energize thesolenoid of drain valve 26 while simultaneously activating reductantpump 22 to prime reductant pump 22 and remove any trapped air inpreparation for an injecting event. In this manner, no injections ofreductant may be unnecessarily wasted during the priming of reductantpump 22. In a fourth condition, based on a signal from temperaturesensor 56, controller 60 may energize the solenoid of drain valve 26while simultaneously activating reductant pump 22 to recirculatereductant and thereby facilitate thawing of reductant.

INDUSTRIAL APPLICABILITY

The disclosed reductant dosing system 14 may be used in any power systemapplication where reductant dosing is required. The disclosed reductantdosing system 14 may provide accurate and repeatable dosing events thatresult in desired quantities of reductant being well-distributedthroughout the exhaust flow 15 entering aftertreatment component 16.Specifically, by utilizing electronically-controlled injectors 24 andproviding these injectors 24 with a stored volume of reductant atprecisely-controlled pressures, it may be easier to adjust dosingfrequency and the dosing may be more accurate and repeatable. Inaddition, electronically-controlled injectors 24 may suffer less frominjector-to-injector variability.

The ability to selectively drain the disclosed reductant dosing system14 may help to prolong component life thereof. In particular, bydraining reservoir 20 at engine shutoff, the likelihood of residualreductant causing clogging or freezing may be reduced. In addition, bydraining reservoir 20 at engine startup as part of a pump-primingprocedure, reductant pump 20 may be rid of air pockets or bubbles thatcan cause unreliable injections without having to waste injections toperform the priming. Further, selective draining of reservoir 20 basedon pressure and temperature may help to control pressures withinreservoir 20 and facilitate thawing.

Because reductant dosing system 14 may be an airless dosing system, itmay be simple and have increased longevity. That is, because reductantdraining and injections may be performed without the assistance ofpressurized air, the components normally required for these purposes canbe eliminated. The resulting system may have fewer components resultinga lower system cost. In addition, the reduction in moving parts mayincrease a durability of the system, resulting in increased longevity.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosed reductantdosing system. Other embodiments will be apparent to those skilled inthe art from consideration of the specification and practice of thedisclosed reductant dosing system. It is intended that the specificationand examples be considered as exemplary only, with a true scope beingindicated by the following claims and their equivalents.

What is claimed is:
 1. A reductant dosing system for an engine,comprising: a supply of reductant; a reservoir configured to holdpressurized reductant, the reservoir being an enclosed chamber; a pumpconfigured to draw reductant from the supply and discharge reductant atan elevated pressure into the reservoir, the reservoir being mounted tothe pump and the pump being mounted to the supply; two injectors fluidlyconnected to the reservoir and configured to independently injectpressurized reductant into exhaust from the engine upstream of anaftertreatment component; an annular mounting member configured to holdthe injectors at equally spaced intervals around an exhaust duct; and acoolant jacket that surrounds and supplies engine coolant to the annularmounting member and the injectors; and a controller in communicationwith the injectors and being configured to activate the injectors toinject pressurized reductant when a pressure of reductant within thereservoir is a desired pressure, wherein the reservoir has an expandablevolume.
 2. The reductant dosing system of claim 1, wherein the reservoirhas a volume expandable to ten times a combined maximum injection amountof the injectors during a single dosing event.
 3. A reductant dosingsystem for an engine, comprising: a supply of reductant; a reservoirconfigured to hold pressurized reductant; a pump configured to drawreductant from the supply and discharge reductant at an elevatedpressure into the reservoir; two injectors fluidly connected to thereservoir and configured to independently inject pressurized reductantinto exhaust from the engine upstream of an aftertreatment component; anannular mounting member configured to hold the injectors at equallyspaced intervals around an exhaust duct; and a coolant jacket thatsurrounds and supplies engine coolant to the annular mounting member andthe injectors; and a drain valve fluidly connected between the reservoirand the supply, wherein the drain valve is electronically controlledbased on at least one of a sensed pressure of the reservoir, atemperature of reductant, and an engine operational status.
 4. Thereductant dosing system of claim 3, further including: a first passageextending from the supply to the pump; and a second passage extendingfrom the drain valve to the first passage.
 5. The reductant dosingsystem of claim 4, wherein the drain valve is disposed within thereservoir.
 6. The reductant dosing system of claim 3, wherein thereservoir has an expandable volume.
 7. The reductant dosing system ofclaim 6, wherein the reservoir has a volume expandable to ten times acombined maximum injection amount of the injectors during a singledosing event.
 8. The reductant dosing system of claim 3, wherein theinjectors are electrically controlled.
 9. The reductant dosing system ofclaim 3, further including a single valve disposed between the pump andthe injectors, the single valve being a check valve.
 10. The reductantdosing system of claim 9, further including a second check valvedisposed between the pump and the supply.
 11. The reductant dosingsystem of claim 3, further including a heater disposed within thereservoir.
 12. The reductant dosing system of claim 3, furtherincluding: a temperature sensor disposed within reservoir; a pressuresensor disposed within the reservoir; and a controller in communicationwith the temperature sensor, the pressure sensor, the pump, and theinjectors, the controller configured operate the pump and the injectorsin response to input from the temperature and pressure sensors.
 13. Thereductant dosing system of claim 3, wherein the reservoir is mounted tothe pump.
 14. The reductant dosing system of claim 13, wherein the pumpis mounted to the supply.
 15. A method of dosing reductant into exhaustof an engine, comprising: drawing reductant from a low-pressure supply;pressurizing reductant; storing pressurized reductant; simultaneouslyinjecting stored reductant at two locations into the exhaust; coolingthe reductant at the two locations of injection; and selectivelydraining stored reductant in response to one of a reductant pressure, areductant temperature, and an engine operational status, whereinselectively draining includes selectively draining stored reductant whenthe engine has been turned off and when the engine has been turned on.